Monday, December 07, 2009

Can This New Wind Turbine Design Save Big Wind?

A new Canadian wind turbine design may actually help make big wind at least semi-feasible. The key is doing away with the gearbox and replacing it with a flywheel and multiple "friction roller" power take-offs.

The gearbox is the heaviest piece of equipment in a wind turbine's "nacelle" (the section at the top of the turbine tower). It's also a piece that's among the most vulnerable to failure. Sudden wind gusts put the gearbox under tremendous mechanical stress. Over time this can wear down or break the teeth off its metal gears.

CWind's design does away with the gearbox completely. Instead, the drive shaft is connected directly to a large metal flywheel. Hugging the outside of the flywheel are eight smaller secondary shafts, each connected to a 250-kilowatt generator and each lined with several specially designed tires that grip the surface of the flywheel. As the flywheel spins, it engages the generators by turning these tire-lined shafts. "We're using friction. It's not mechanically hard-coupled," says Na'al Nayef, a CWind engineer and co-inventor of the system.

Nayef says the system uses software to control the eight secondary shafts. The tires are also designed to temporarily slip if a wind gust causes the flywheel to suddenly speed up. This feature eases the impact on the generators. Each secondary shaft can also be disengaged from the flywheel if the wind slows down, in effect reducing friction and allowing shafts that are still connected to keep their generators operating at high capacity. Likewise, connecting more shafts, thus adding more friction when the wind increases, will engage idle generators. "We can operate the generators at optimal speed all the time," says Nayef, adding that tests on the smaller, 65-kilowatt prototype show efficiency gains over standard wind turbines of up to 5 percent.

...the tires used are designed to last for three years, and replacing all the tires used on a two-megawatt wind turbine is expected to cost $30,000--or nearly $200,000 over 20 years. By contrast, gearboxes have an average life of six years and cost about $600,000 to replace, or nearly $2 million over 20 years. "We're going to be competitively priced with conventional gearbox wind turbines, yet we have the advantages of high availability, high efficiency, and all of the advantages that come with serviceability." _Technology Review

Huge, expensive gearboxes set out in the elements? What moron "engineer" dreamed up that idea? And they even want to put these delicate gearboxes offshore, in a salty water vapour environment? How stupid is that?

The new friction based transmissions make a lot more sense. Whether they can tip the balance enough to make big wind profitable or not is another question. Until utility-scale power storage comes along to provide scalable load-leveling, it is a big question mark.

Either way, nuclear baseload power makes far more sense for large power needs in most parts of the world.